: an elementary particle that is identical with the nucleus of the hydrogen atom, that along with the neutron is a constituent of all other atomic nuclei, that carries a positive charge numerically equal to the charge of an electron, and that has a mass of 1.673 × 10−27 kilogram
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Now, most of the atoms in the universe are the two simplest kinds: hydrogen, which has one proton, zero neutrons and one electron; and helium, which has two protons, two neutrons and two electrons.
—
Stephen L. Levy, The Conversation, 23 June 2025
First, the two colliding protons each emit a W boson, a particle associated with the weak nuclear force.
—Matt Von Hippel, ArsTechnica, 23 June 2025
Beyond electrons, the quarks that make up protons and neutrons in atomic nuclei are also fermions.
—Matt Von Hippel, Quanta Magazine, 23 June 2025
This situation changed when the universe had expanded and cooled enough to allow electrons to bond with protons and create the first neutral atoms of hydrogen.
—Robert Lea, Space.com, 11 June 2025
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Stephen L. Levy, The Conversation, 23 June 2025
First, the two colliding protons each emit a W boson, a particle associated with the weak nuclear force.
—Matt Von Hippel, ArsTechnica, 23 June 2025
Beyond electrons, the quarks that make up protons and neutrons in atomic nuclei are also fermions.
—Matt Von Hippel, Quanta Magazine, 23 June 2025
This situation changed when the universe had expanded and cooled enough to allow electrons to bond with protons and create the first neutral atoms of hydrogen.
—Robert Lea, Space.com, 11 June 2025
See All Example Sentences for proton
Cite this Entry
“Proton.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/proton. Accessed 6 Jul. 2025.
Copy CitationKids Definition
proton
noun
pro·ton
ˈprō-ˌtän 
: an atomic particle that occurs in the nucleus of every atom and carries a positive charge equal in size to the negative charge of an electron
Medical Definition
proton
noun
pro·ton
ˈprō-ˌtän
: an elementary particle that is identical with the nucleus of the hydrogen atom, that along with neutrons is a constituent of all other atomic nuclei, that carries a positive charge numerically equal to the charge of an electron, and that has a mass of 1.673×10−24 gram
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